In recent years, DRAM-embedded devices in which a high-performance logic circuit and a DRAM memory are combined together have been made practical for multimedia devices requiring miniaturization, a high memory capacity and a high data transfer rate. The DRAM-embedded devices are broadly classified into a trench capacitor type in which a capacitor as an information storage unit of a DRAM memory cell is provided in a trench of a semiconductor substrate and a stack capacitor type in which a capacitor and an electrode are three-dimensionally stacked above a principal surface of a semiconductor substrate.
On the other hand, attention is again focused on a device in which a so-called planar (MOS structure) DRAM and a logic circuit are merged using a gate dielectric as a capacitance dielectric and a gate electrode as a plate electrode, because it is a device in which a memory cell can be formed more easily.